org.apache.xmlgraphics.image.codec.util.ForwardSeekableStream Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: ForwardSeekableStream.java 1732018 2016-02-24 04:51:06Z gadams $ */
package org.apache.xmlgraphics.image.codec.util;
import java.io.IOException;
import java.io.InputStream;
/**
* A subclass of SeekableStream that may be used
* to wrap a regular InputStream efficiently.
* Seeking backwards is not supported.
*
*/
public class ForwardSeekableStream extends SeekableStream {
/** The source InputStream. */
private InputStream src;
/** The current position. */
long pointer;
/**
* Constructs a InputStreamForwardSeekableStream from a
* regular InputStream.
*/
public ForwardSeekableStream(InputStream src) {
this.src = src;
}
/** Forwards the request to the real InputStream. */
public final int read() throws IOException {
int result = src.read();
if (result != -1) {
++pointer;
}
return result;
}
/** Forwards the request to the real InputStream. */
public final int read(byte[] b, int off, int len) throws IOException {
int result = src.read(b, off, len);
if (result != -1) {
pointer += result;
}
return result;
}
/** Forwards the request to the real InputStream. */
public final long skip(long n) throws IOException {
long skipped = src.skip(n);
pointer += skipped;
return skipped;
}
/** Forwards the request to the real InputStream. */
public final int available() throws IOException {
return src.available();
}
/** Forwards the request to the real InputStream. */
public final void close() throws IOException {
src.close();
}
/**
* Forwards the request to the real InputStream.
* We use {@link SeekableStream#markPos}
*/
public final synchronized void mark(int readLimit) {
markPos = pointer;
src.mark(readLimit);
}
/**
* Forwards the request to the real InputStream.
* We use {@link SeekableStream#markPos}
*/
public final synchronized void reset() throws IOException {
if (markPos != -1) {
pointer = markPos;
}
src.reset();
}
/** Forwards the request to the real InputStream. */
public boolean markSupported() {
return src.markSupported();
}
/** Returns false since seking backwards is not supported. */
public final boolean canSeekBackwards() {
return false;
}
/** Returns the current position in the stream (bytes read). */
public final long getFilePointer() {
return pointer;
}
/**
* Seeks forward to the given position in the stream.
* If pos is smaller than the current position
* as returned by getFilePointer(), nothing
* happens.
*/
public final void seek(long pos) throws IOException {
while (pos - pointer > 0) {
pointer += src.skip(pos - pointer);
}
}
}